Hydrothermal vents are fissures in the earth's surface from which geothermally heated water issues. Such hydrothermal vents are commonly found near volcanically active locations, areas associated with movement of tectonic plates and ocean basin hotspots. Plumes emanating from hydrothermal vents include minerals and gases such as hydrogen, methane, carbon dioxide and hydrogen sulfide. Since methane and carbon dioxide are known to be greenhouse gases, gases emitted from the hydrothermal vents are believed to contribute to greenhouse warming. Furthermore, the relatively high temperature of the water emitted from hydrothermal vents is conducive to formation of aquacultures including anaerobic microorganisms. Such anaerobic microorganisms consume carbon dioxide, as an energy source, from the seawater as well as that emitted by the hydrothermal vents and convert it into methane. Methane is the principal component of natural gas and its relative abundance enhances its attraction as an alternative fuel source.
“Economic Geology of Natural Gas Hydrate”, M. D. Max et al. (“Max” hereafter) teaches that several kinds of pore holes in the sedimentary sea floor exist, including the hydrothermal vents. Chapter 4 of Max discusses the detailed working of hydrothermal vent mechanisms. FIG. 4.3 of Max shows a schematic of the sedimentary features for collisional continental margins. Different mechanisms are responsible for the release of methane from the sediment into the pore holes for Thermo-Genic (TG) and Bio-Genic (BG) pore holes. FIG. 4.4 of Max shows a schematic of the sedimentary features for a passive continental margin. The TG pore holes are commonly called hydrothermal vents. However, there are other conditions (for example, FIG. 3.21 of Max) that typically are more transient in nature where a subsiding seafloor can allow BG pore holes to form, thus releasing methane gas into the ocean.
As is known in the art, carbon dioxide and other gases stay dissolved in the relatively high temperature, high pressure water issuing from hydrothermal vents. Some gasses such as methane are not dissolved. As the relatively high temperature vent water comes in contact with the ambient (relatively cold) water surrounding the vents, the vent water is cooled. The cooling vent water causes methane and other gases to diffuse into the surrounding water. The diffusion of these gases makes it difficult to harvest these gases from the vent water.
“Marine Geochemistry” by Schultz, et. al, (“Schultz” hereafter) provides detailed descriptions of the minerals, and their chemistry, present in the sea floor sediments, which are leached out into the vent fluid and present in the plumes. For example, chapter 3 of Schultz discusses the dissolved constituents in marine pore water, chapter 4 of Schultz discusses the organic matter accumulation in sediments and organic geochemical processes, and chapter 5 of Schultz describes bacteria and marine biogeochemistry. Schultz also describes the reactivity of iron (chapter 7), the sulphate reduction (chapter 8), the carbonates (chapter 9), the availability of manganese (chapter 11) and hot vents and cold seeps (chapter 13) as applicable to the marine geology.
Systems and methods for harvesting gases and minerals from hydrothermal resources are desirable.